Limited engagement lug assembly



United States Patent 3,344,394 LHVIITED ENGAGEMENT LUG ASSENIBLY Benjamin S. Kingsbury, Pasadena, and Reginald E. Lockhart, Los Angeles, Calif., assignors to Zinsco Electrical Products, Los Angeles, Calif., a corporation of California Filed May 16, 1966, Ser. No. 550,323 Claims. (Cl. 339-272) ABSTRACT OF THE DISCLOSURE A lug assembly particularly suited for connecting a solid aluminum wire to an electrical switch. A tubular shell lug with a notched conductor bar positioned therein below inwardly projecting integral ridges which engage and limit movement of a clamp screw.

This invention relates to a lug assembly and more particularly to a lug assembly for use in electrical circuit devices, particularly breakers and switches.

Many problems arise in the ostensibly simple task of interconnecting electrical conductors. For example, in securing a circuit breaker or a switch or other electrical device to a wire of an external circuit, it is important to obtain a mechanically strong connection so that the wire will not become inadvertently detached from the device. A strong connection is particularly difficult to obtain when the conductor is made of a relatively soft deformable material such as aluminum. The typical clamping device which is manually turned down against the deformable conductor often deforms the wire beyond the acceptable limit and may even sever the wire. On the other hand, connectors that do not permit severing 0f the wire may not in every instance form a strong connection. Another difiiculty with prior art connectors is the problem of maintaining proper alignment of the conductors within the connector.

A primary object of this invention is to provide a switch lug assembly which will form a strong connection between two conductive members yet positively limit deformation of the conductors.

A further object of this invention is to provide a switch lug assembly which will firmly clamp a deformable conductor against a conductive member but will positively prevent severing of the deformable conductor by the connector.

Another object is to provide a lug assembly which can be readily used with a deformable conductor such as aluminum or a relatively nondeformable conductor such as copper.

A further object of this invention is to provide a lug assembly which will positively align the conductors which are interconnected thereby and one in which the lug will be no wider than the conductor bar.

Still another object of this invention is to provide an inexpensive lug assembly which is easily assembled and one in which the components thereof can be firmly held in the assembled condition by a single screw.

The invention includes a lug having a passageway extending therethrough and a conductor bar seated against a bearing surface of the passageway. A conductor, which may be of soft deformable material, also extends into the passageway of the lug and is clamped against the conductor bar by a threaded member which extends through a threaded aperture in one wall of the lug. Movement of the threaded member toward the conductor is limited by an abutment which is integral with the lug and extends into the passageway thereof. Thus, the threaded member may be moved toward the conductor until it engages the abutment, at which point the conductor will be firmly 3,344,394 Patented Sept. 26, 1967 clamped against the conductor bar. The abutment is positioned within the passageway so that the deformable conductor will not be severed or unduly deformed when the threaded member engages the abutment.

To prevent movement of the conductor bar axially in the passageway of the lug, the conductor bar is provided with a pair of opposed notches in the periphery thereof. These notches define opposed locking surfaces which engage the end surfaces of the lug.

To maintain the conductor bar and the conductor in proper alignment, the conductor bar is formed with a longitudinally extending groove for receiving the conductor. To facilitate manufacturing, the lug is preferably an extruded aluminum shell. If desired, the switch lug assembly may be used in an electrical switch or in a circuit breaker to connect the switch or circuit breaker to the wires of an external circuit.

The invention, both as to its organization and method of operation together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a top plan view of a circuit breaker embodying the switch lug assembly of this invention;

FIG. 2 is a side elevational view of the circuit breaker with portions thereof broken away to expose the switch lug assembly, which is also shown in side elevation;

FIG. 3 is an enlarged fragmentary sectional view taken along line 33 in FIG. 2 and showing the switch lug assembly clamping a deformable conductor to a conductor bar; and

FIG. 4 is an enlarged exploded isometric View of the lug and a portion of the conductor bar.

FIGS. 1 and 2 illustrate a circuit breaker 11 in which a switch lug assembly 13 may be utilized. The lug assembly 13 may be utilized in various types of switches and electrical devices, the circuit breaker of FIGS. 1 and 2 being shown by way of illustration only.

The lug assembly 13 includes an extruded aluminum lug or tubular shell 15, a conductive member or conductor bar 17, and a threaded member or screw 19. The conduct-or bar 17 is an elongated thin strip of conductive metal which is bent at a right angle intermediate its ends as shown in FIG. 2. p 7 v The conductor bar 17 has a bearing surface 21. and an opposed clamping surface 23 with a longitudinally extending groove 25 therein. As best seen in FIG. 4, the clamping surface 23 at one end is not planar and slopes downwardly toward the longitudinal groove 25. Intermediate the bend and one end of the conductor bar 17 a pair of opposed peripheral notches 27 and 29 is formed. Each of the notches defines a pair of opposed transverse locking surfaces 31. The other leg of the conductor bar has a pair of threaded openings 33 (only'one being shown in FIG. 4).

The lug 15 is generally rectangular in cross section and has an axial generally rectangular passageway 35 extending therethrough, the lower surface of the passageway defining a bearing surface 37. Opposed abutments or ridges 39 are extended integrally with the lug and extend into the passageway 35 throughout the entire length thereof.

A threaded aperture 41 is formed in the upper wall of- 3 passageway 35. Thus, in the assembled position the lug 15 and the conductor bar 17 are as shown in FIGS. 2 and 3.

In the assembled condition, the bearing surfaces 21 and 37 are in engagement and the clamping surface 23 is exposed in the passageway 35 and faces upwardly toward the threaded aperture 41. As shown in FIG. 3, the conductor bar 17 fits loosely within the passageway 35 and the clamping surface 23 is preferably spaced downwardly slightly from the lower edges of the abutments 39.

A conductor 45 which may be constructed of a soft conductive material such as aluminum is also inserted into the passageway 35 and engages the groove 25 which aligns the conductor with the conductor bar 17. The screw 19 extends through the threaded aperture 41 and may be turned downwardly to apply a force to the conductor 45 to firmly clamp the latter against the clamping surface 23. The screw 19 serves as a clamping member for clamping the conductor 45 in position and for retaining the conductor within the groove 25. Preferably the axes of the screw 19 and the passageway 35 are generally perpendicular. The abutments 39 are so positioned within the passageway 35 that the lower surface of the screw 19 will be in engagement therewith when the conductor 45 has been deformed a limited predetermined amount. The abutments 39 positively limit the amount the conductor 45 can deform in response to the force applied thereto by the screw 19 and also prevent severing of the conductor 45 by the screw. The switch lug assembly 13 may also be used with nondeformable conductors, in which case the screw 19 will not necessarily come into engagement with the abutments 39 in normal use thereof.

In the assembled condition of the lug assembly shown in FIGS. 2 and 3, the locking surfaces 31 of the conductor bar 17 are closely adjacent and engageable with the end surfaces 43 of the lug 15 to substantially prevent axial movement of the conductor bar relative to the lug. When the screw 19 is turned down to the position shown in FIG. 3, it forces the bearing surfaces 21 and 37 into tight frictional engagement to prevent all relative movement between the lug 15 and the conductor bar 17. Thus, all of the components of the switch lug assembly 13 are held firmly together by the screw 19.

As shown in FIGS. 1 and 2, the lug assembly 13 is particularly adapted for use with the circuit breaker 11. The circuit breaker 11 includes a housing 47, the usual bus bar connector 49, and an opening 51 through which the conductor 45 may be inserted. A pair of screws 53 passes through the two threaded openings 33 in the conductor bar 17 to secure the switch lug assembly 13 within the housing 47. The housing 47 may be constructed of an insulating plastic material and includes two housing sections 55 and 57. The housing section 55 has three surfaces 59, 61, and 63 projecting into the interior of the housing to further support the conductor bar 17. The housing section 57 is formed with similar surfaces (not shown) to firmly retain the switch lug assembly 13 within the housing 47. An internal conductor 65 may be secured to the conductor lug 17 within the housing 47 by any suitable means, typically by welding.

The lug assembly 13 when used as described herein will firmly secure the circuit breaker 11 to the conductor 45 without unduly deforming or severing this conductor. The conductor 45 is firmly clamped in the groove 25 which establishes and maintains alignment of the conductor 45. The entire lug assembly 13 is very inexpensive and easy to assemble, and all of the parts thereof are held together in the assembled position by the screw 19. By positioning the screw 19 closely adjacent or in engagement with the abutments 39, the conductor bar 17 cannot be withdrawn from the passageway 35 even though the conductor 45 is not in the lug assembly.

The lug assembly permits a narrow construction wherein the lug 15 need not be wider than the conductor bar 17. The lug configuration with constant cross section is ideally suited for manufacturing by extruding, but the lug abutments 39 could be formed by punching if desired. It should be noted that the two abutments 39 need not be the same size and one may be omitted in some instances. Similarly the notches 27, 29 need not be the same size and one may be omitted, corresponding to the lug shape. The assembly provides direct mechanical clamping between the conductor and the conductor bar, hence the lug and screw need not be of electrical conducting material.

Although an exemplary embodiment of the invention has been disclosed herein, it should be understood that many changes, modifications, and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

What is claimed is:

1. In a lug assembly adapted for electrically interconnecting a first conductor with a second conductor, the combination of:

a conductive member having a bearing surface and a clamping surface, said conductive member being connectible to the first conductor;

a lug having a passageway therethrough, said passageway having a bearing surface, said conductive member being received in said passageway with said hearing surface of said conductive member abutting against said bearing surface of said passageway, said clamping surface of said conductive member being exposed in said passageway, the second conductor being receivable on said clamping surface;

clamping means secured to said lug and being movable toward said clamping surface of said conductive member for applying a force to the second conductor to firmly clamp the latter against said clamping surface; and

abutment means in said passageway spaced from said lug bearing surface engageable with said clamping means for limiting the minimum distance between said clamping means and said clamping surface of said conductive member to thereby positively limit the amount the second conductor can deform in response to said force and prevent severing of the second conductor by the clamping means.

2. A combination as defined in claim 1 wherein said lug includes a tubular shell, said abutment means includes two opposed ridges integral with said shell and extending along said passageway, and said clamping means includes a threaded member received by said tubular shell.

'3. A combination as defined in claim 1 wherein said conductive member is a conductor bar, said conductor bar has a pair of opposed notches formed along the periphery thereof, each of said notches defining a pair of opposed locking surfaces, said lug includes a tubular shell having a pair of end surfaces, said notches of said conductor bar being received within said passageway with said locking surfaces of said conductor bar being engageable with said end surfaces of said shell to substantially prevent axial movement of said conductor bar relative to said shell, and wherein said conductor bar has a longitudinally extending groove for receiving the second conductor, the second conductor being alignable by said groove and retainable therein by said clamping means, said clamping means including a threaded member which passes through a threaded aperture in said shell, the axes of said threaded member and said passageway being generally perpendicular, and said abutment means includes a pair of opposed ridges integral with said shell and extending throughout the length of said passageway.

4. In a switch connectible to a conductor, the combination of:

a housing; a conductive member having a bearing surface and a clamping surface;

means for securing said conductive member in said housing;

conductive means in said housing secured to said conductive member;

a lug having a passageway therethrough, said passageway having a bearing surface, said conductive member being received in said passageway with said bearing surface of said conductive member abutting against said bearing surface of said passageway, said clamping surface of said conductive member being exposed in said passageway, the conductor being receivable on said clamping surface;

clamping means secured to said lug and movable toward said clamping surface of said conductive member for applying a force to the conductor to firmly clamp the latter against said clamping surface; and

abutment means in said passageway spaced from said lug bearing surface engageable with said clamping means for limiting the minimum distance between said clamping means and said clamping surface of said conductive member to thereby positively limit the amount the conductor can deform in response to References Cited UNITED STATES PATENTS 3,029,410 4/ 1962 Cornell 339-272 3,075,039 1/ 1963 Kobryner 317-119 FOREIGN PATENTS 603,254 8/1960 Canada. 1,352,160 1/1964 France. 1,356,171 2/1964 France.

ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner. 

1. IN A LUG ASSEMBLY ADAPTED FOR ELECTRICALLY INTERCONNECTING A FIRST CONDUCTOR WITH A SECOND CONDUCTOR, THE COMBINATION OF: A CONDUCTIVE MEMBER HAVING A BEARING SURFACE AND A CLAMPING SURFACE, SAID CONDUCTIVE MEMBER BEING CONNECTIBLE TO THE FIRST CONDUCTOR; A LUG HAVING A PASSAGEWAY THERETHROUGH, SAID PASSAGEWAY HAVING A BEARING SURFACE, SAID CONDUCTIVE MEMBER BEING RECEIVES IN SAID PASSAGEWAY WITH SAID BEARING SURFACE OF SAID CONDUCTIVE MEMBER ABUTTING AGAINST SAID BEARING SURFACE OF SAID PASSAGEWAY, SAID CLAMPING SURFACE OF SAID CONDUCTIVE MEMBER BEING EXPOSED IN SAID PASSAGEWAY, THE SECOND CONDUCTOR BEING RECEIVABLE ON SAID CLAMPLING SURFACE; CLAMPING MEANS SECURED TO SAID LUG AND BEING MOVABLE TOWARD SAID CLAMPING SURFACE OF SAID CONDUCTIVE MEMBER FOR APPLYING A FORCE TO THE SECOND CONDUCTOR TO FIRMLY CLAMP THE LATTER AGAINST SAID CLAMPING SURFACE; AND ABUTMENT MEANS IN SAID PASSAGEWAY SPACED FROM SAID LUG BEARING SURFACE ENGAGEABLE WITH SAID CLAMPING MEANS FOR LIMITING THE MINIMUM DISTANCE BETWEEN SAID CLAMPING MEANS AND SAID CLAMPING SURFACE OF SAID CONDUCTIVE MEMBER TO THEREBY POSITIVELY LIMIT THE AMOUNT THE SECOND CONDUCTOR CAN DEFORM IN RESPONSE TO SAID FORCE AND PREVENT SEVERING OF THE SECOND CONDUCTOR BY THE CLAMPING MEANS. 